Disable snappy support by default in compilation

Snappy/Compression will not be a feature of server 3.0

Change-Id: Ic5d0625e73a19a24a652ef3100d841e4724f3fc8
Reviewed-on: http://review.couchbase.org/38525
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>